Radio antenna for automobiles



April 20, 1937. A. D. BAKER RADIO ANTENNA FOR AUTOMOBILES Filed June 26, 1956 Patented Apr. 20, 1937 PATENT OFFlQE RADIO ANTENNA FOR AUTOMOBILES Albert D. Baker, Lansing, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application June 26, 1936, Serial No. 87,330

4 Claims.

This invention relates to the use of a metal portion of an automobile running board as a radio antenna.

It has heretofore been suggested to use the 5 main metal portion of a rubber-covered running 10 portion and the step-hangers.

Applicant has discovered that a great improvement in radio reception or antenna pick-up may be had if the step-hangers themselves be insulated from the chassis side rail as well as from 5 all other metal parts of the automobile. Such step-hangers extend transversely across and underlie the main metal portion of the running board, and, if such step-hangers are not insulated from the metal of the chassis frame, for some reason they cause a peculiar decrease in the signal pick-up of said insulated main metal portion when used as a radio antenna even tho said main metal portion befully insulated and materially spaced from the step-hangers.

An object of this invention therefore is to provide a running board structure used as an antenna wherein the underlying step-hangers are electrically insulated from the chassis side rail which supports them. The beneficial effects of so insulating the step-hangers themselves are realized both when the main metal portion of the board is insulated from the hangers and when said main metal portion is not insulated from the hangers. Obviously when said main metal portion is not insulated from the hangers the metal of the trans- D verse hangers is electrically one with the main metal portion and so forms part of the antenna. Another object of this invention is to provide a very simple and strong attachment means for insulatingly fixing the step-hangers to the chassis side rail, which attachment means gives only a very small shunt capacity between the metal of the chassis and the metal of the antenna. Such shunt capacity is harmful since it reduces effective signal pick-up and hence should be kept to a a minimum. The attachment means of this invention gives such small shunt capacity by providing only relatively small areas of the transversely-pro-jecting step-hangers which are in fairly close proximity to the metal of the chassis frame. In other words, the main relatively wide area of the antenna metal is laterally off-set a considerable distance from the side rail and hence has a very small harmful shunt capacity therewith,

, which wide area of antenna metal however is 0 properly supported to be used as a step by the relatively narrow-inwardly-projecting ends of the step-hangers which from practical necessity must lie fairly close to the metal side rail.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of the present invention is clearly shown.

In the drawing:

Fig. l is a plan view of an insulated automobile running board mounted according to this inven tion and used as a radio antenna.

Fig. 2 is a vertical section on line 2-2 of Fig. l and shows structural details of the insulated mounting.

Fig. 3 is a vertical section on line 3-3 of Fig. 2 and shows one method of securing the running board proper to the metal step-hangers without electrical insulation therebetween.

Similar reference characters refer to similar parts throughout the several views.

l0 designates an ordinary channel section side rail of the automobile chassis frame which serves as a support for the running board which is designated as a whole by reference numeral l l. Board II is spaced from and laterally offset from side rail l0 and is supported directly upon two transversely extending step-hangers l2, whose inner end portions I3 project a considerable distance beyond the inside margin M of the main sheet metal portion l5 ofboard H and are fixed to but insulated from the side rail I0 in such a manner that these hangers I2 can readily support the down load of persons standing on the running board.

A feature of this invention is the strong but nevertheless insulated attachment of hangers 12 to the side rail H). In the form shown in Fig. 2 of the drawing, the inner end It of each of hangers I2 is rigidly bolted to the bottom flange ll of side rail 1 0 by bolt l8 and metal washer l9 and an interposed electrical insulator '28. This insulator 20 is preferably made in two parts as shown and may be of any suitable electrical insulating material such as electrical insulating fiber, bakelite, hard rubber, micarta or bakelite reinforced with cotton fabric or fibers and molded under heat and pressure. This inner end attachment by bolt l8 however would not be sufiiciently strong to properly support the down load on the running board I I. A further strengthening support for hanger I2 is therefore provided by the metal tension member 25 which is approximately of the same relatively narrow width as hanger l2. Member 25 is rigidly riveted to side rail ill by rivets 26 and is shaped as shown in Fig. 2 so that its outer lower end 21 provides a point of attachment for hanger I 2 spaced a considerable distance from the attachment bolt l8. Hanger I2 is insulatedly fixed to the lower end 21 of member by means of bolt l8 and insulator 20' which may be the same or similar to the attachment at bolt l8 as above described. Thus it will be seen that hanger l2 has its inwardly projecting portion l3 insulated from the side rail l0 yet very strongly fixed thereto so that it can properly sustain the down load on the running board II, and at the same time the relatively wide area of the main metal sheet l5 of the board I l is held spaced a considerable distance from the longitudinally-extending side rail l0 and from any other body metal parts. This greatly reduces harmful shunt capacity between the main metal sheet l5 and other grounded metal parts, as described above. Even though in the form illustrated in drawing, sheet I5 is electrically connected to hanger l2 and these hangers [2 are only narrowly spaced from rail Ill and tension member 25, the shunt capacity between the insulated antenna and side rail I0 is kept small due to the relatively narrow areas of the projecting portions l3 which from practical necessity extend fairly close to rail I0 and the grounded metal member 25.

In the form illustrated, the running board H comprises a main metal sheet l5 having a molded resilient rubber covering 9 vulcanized thereto and providing a. suitable step-covering and also electrical insulation for the entire upper surface of the sheet l5. Covering 9 extends upwardly beyond the inner margin I4 of sheet l5 and forms an integrally molded flexible non-metal closure flap for the longitudinally extending space between said inner margin M of metal sheet l5 and the lower edge of the metal body panel 32. The resilient rubber lip 3| of closure flap- 3E! is preferably held snugly against the small flange 33 fixed to the lower edge of the body panel by pressure put thereupon when board I is finally assembled in place upon the step-hangers [2. This non-metal closure flap 30 should be of such width as to provide the necessary spacing between metal sheet I 5 and the metal panel 32. The ends or" board l i are shown in Fig. 1 as being properly spaced at 35 from the adjacent metal fenders 36 and 31. The integrally molded flexible rubber closure flap 30 preferably has projecting end portions 40 (see Fig. 1) which are molded to shape so as to snugly engage a portion of the adjacent ends of fenders 36 and 3'! and form a neat joint therewith. If desired the open spaces 35 between the metal fenders 36 and 31 and the two ends of the metal sheet I5 may be completely closed by integrally molded flexible rubber end flaps which in effect form continuations around the two ends of board ll of the flexible rubber closure flap 39.

The main metal sheet l5 has fixed to its under side by welding or other suitable means two longitudinal metal channels 50 for greatly stifiening and strengthening the running board. Channels 50 each have short metal inverted channels 5! welded thereto where they cross the two stephangers I2, which inverted channels 5i are bolted directly to hangers l 2 by the bolts 52 as shown in Figs. 2 and 3. Fig. 3 shows how the sides of the inverted channel 5| are spot welded to the depending flanges of channel 50 at the points 53. The bottom web 54 of inverted channel 5| has a hole 55 therein large enough to pass the head of bolt 52 therethru and a connecting elongated slot 56 which serves as an adjusting slot thru which the shank of bolt 52 passes after its head has been passed thru hole 55 to lie above the web 54. It will now be seen that all the attaching bolts 52 may be easily inserted in approximate position in the inverted channels 5i before the board placed uponthe hangers 2. The bolt heads are retained temporarily in place by a friction contact with the metal lip 57 which is formed from the metal cut out in making the elongated slot 58, as will be clear from Fig. 3. After all the bolts 55. have been inserted in the inverted channels 55 as above described, the board l l is simply set down upon the two step-hangers 62 (which have been previously fixed to the side rail 15 as above described) and the threaded shanks of bolts 52 inserted thru holes provided therefor in the hangers l 2 and then the nuts 58 are applied and tightened. When board 5 l is so placed in position and fastened to the hangers l2 the flexible rubber closure lip 30 will be pressed into snug contact with the flange 33 at the lower margin of body panel 32 and will be thus retained in place without further fastening means. Of course any other suitable means for fixing board I l to the hangers !2 may be used if desired. In the form illustrated in the drawing the antenna is composed of the metal sheet l5 and its attached metal parts which includes channels 50 and hangers [2. The metalshielded antenna lead 6i! (see Fig. 1) may be bolted and soldered to one of the metal channels 50 or directly to the metal sheet [5.

As explained hereinabove, the electrical insulation of step-hangers I2 is also highly advantageous when it is desired to also insulate the metal sheet l5 from the hangers l2. In cases where the metal sheet I5 is also insulated from the hangers l2 by electrical insulator blocks interposed between these parts there ordinarily results some further decrease in the shunt capacity between the antenna proper and the other metal parts of the chassis or body. This further advantage may or may not be desired in any given case due to the extra cost of providing suitable electrical insulation between the main metal sheet of the running board and the step-hangers therefor.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In an automobile, a metallic chassis-frame side rail, a series of transversely-extending outwardly-projecting metal hangers securely fixed to said side rail, said hangers being electrically insulated from said side rail, a running board mounted upon the outer portions of said hangers and supported thereby, said running board comprising a metal member having a substantial plan area overlying said hangers and held in spaced relation to all grounded metal parts of the automobile and serving as a radio antenna.

2. In an automobile, a metallic chassis-frame side rail, a plurality of transversely-extending outwardly-projecting metal hangers securely fixed to said side rail, relatively small electrical insulators interposed between said hangers and side rail and insulating said hangers from said side rail, a running board supported upon the outer portions of said hangers and having a main metal member held substantially spaced from all grounded metal parts of the chassis and body and serving as a radio antenna.

3. In an automobile having a metal chassisframe side rail, in combination, two transversely-extending outwardly-projecting metal hangers having their inner end portions fixed to said side rail by means of electrical insulators, metal tension members fixed to said rail and extending outwardly therefrom and having their outer ends fixed to said hangers at an intermediate portion thereof by means of electrical insulators, a running board supported upon the outwardly extending portions of said hangers, said board having a main metal member held substantially spaced from all grounded metal parts of the chassis and body and serving as a radio antenna.

4. In an automobile, a metallic chassis-frame side rail, a plurality of transversely-extending outwardly-projecting metal hangers securely fixed to said side rail and supported thereby, said hangers being electrically insulated from said side rail, a running board mounted upon the outwardly-projecting portion of said hangers and supported thereby, said running board comprising a metal member overlying said hangers and electrically insulated from all grounded metal parts of the chassis and body and serving as a radio antenna.

ALBERT D. BAKER. 

